In the general state of the art of electrical and electronic systems housed in cabinets (often termed chassis), there are typically inputs and outputs to the system, facilitated by connection of communication links of various sorts, over which signals are received and sent. There are also numerous situations wherein groups of components in a chassis have to be connected to and communicate with other groups of components internally. Data routers in packet networks, such as the well-known Internet, are a good example. In description in this specification a data router is used as a specific example of such a situation, and the present invention in several aspects is applicable to such routers.
Transmission of network data traffic is accomplished with the use of data routers as introduced above. A physical data routing machine typically consists of a processing unit or multiple units which are housed in a chassis and which communicate with each other and with other data routing machines.
In prior art, one method for achieving communication between processing units in a single chassis, such as in a data router, involves the use of an electrical backplane. When communication between multiple chassis is required, the electrical backplanes of the chassis have been connected by cables. The electrical backplane is commonly implemented as a printed circuit board assembly which provides electrical connectivity between processing units.
Noting that it may sometimes be desirable to communicate at backplane level between elements that are not closely physically associated, such as between elements that may be mounted in separate physical electronic cabinets, there is a potential problem with electrical backplanes. When an electrical signal is transmitted over relatively long distances, for example, deterioration of the signal may occur for any of several reasons. For example, longer signal paths necessarily present additional resistance. Also, longer paths present additional opportunity for interference. Therefore, in order to transmit clean signals in systems utilizing electrical backplanes the elements in communication must be in relatively close physical proximity to one another, such as in the same cabinet.
Another drawback to electrical backplane boards is that they are relatively difficult to service. One reason is that the conductors for the electrical signals are typically patterned on the board, and individual conductors (signal paths) cannot be separately serviced. In many cases the backplane boards are also hardwired to other components. Because any change or repair is normally via a replacement of the entire backplane, the system containing the electrical backplane is generally out of service during any backplane service.
What is clearly needed is an apparatus and method enabling cleaner data signal transmission between router processing units while at the same time facilitating easier manufacturing and off-line servicing of backplane assemblies.